This invention relates to a cleaning unit for removing residual toner adhering onto an image support or a paper support in an image formation unit such as an electrophotographic copier or a laser beam printer and in particular to a cleaning unit having transport means disposed in a storage vessel and using information of a turn state, etc., of the transport means to sense that the storage vessel fills with collected toner.
An image formation unit using an electrophotographic system for preparing record paper, such as an electrophotographic copier or a laser beam printer, is provided with a cleaning unit for removing residual toner adhering to the surface of a photosensitive drum after a toner image is formed for an image support such as a photosensitive drum and is transferred to paper. Known as the cleaning unit are, for example, a cleaning unit using a blade as disclosed in Japanese Utility Model Laid-Open No. Sho 64-38668, etc., and a cleaning unit using a blade and a rotating brush as disclosed in Japanese Utility Model Laid-Open No. Sho 62-170967. As shown in the conventional examples, the operation of pressing the blade against the photosensitive drum surface for scraping off toner and the operation of operating the two members of the blade and brush for removing residual toner can be performed.
In the conventional examples, the image formation unit uses a photosensitive drum as an image support. To an image formation unit using a photosensitive belt as an image support, a cleaning unit using a rotating brush and a blade is also applied, for example, as disclosed in Japanese Utility Model Laid-Open No. Hei 1-181056. In the example of the cleaning unit applied to the photosensitive belt, means for transporting collected toner is placed at a position where toner in the lower part of the main unit of the cleaning unit drops, and a long pipe containing a screw is connected for transporting toner to a collection box placed at a position away from the main unit. Further, in the conventional example, means for sensing that the toner collection box fills with toner is placed and when the collected toner stored in the toner collection box reaches a predetermined amount, the collection box is replaced with a new one. When the toner collection box is placed at a position away from the main unit of the cleaning unit as in the conventional example, the toner collection box space need not be near the photosensitive member, thus the housing space of other components placed corresponding to the photosensitive member is not affected.
Sensing means such as a sensor is placed near the vessel storing collected toner shown in the conventional example and is used to sense that the collected toner accumulated in the vessel reaches a predetermined level. However, even if toner is stored in the collection vessel on one side, when the toner is sensed by the sensor, a full signal is output for instructing the operator to replace the collection box. Apart from the conventional example, in an example disclosed in Japanese Patent Laid-Open No. Sho 60-230178, etc., transport means is connected to the lower part of a toner collection box, collected toner is stored from the lower part of the vessel, and the toner stored in the vessel can be stored in a pressure seal condition.
In the conventional example, an optical sensor of transmission type is placed in the upper part of the collection box is placed and when toner is pushed up to a predetermined height, the optical sensor can sense that the collection box fills with the toner. When the main unit of the cleaning unit and the collection box are placed separately as in the conventional example, a transporter for transporting toner needs to be added between the two members; the configuration can be easily applied to a large unit. However, for a cleaning unit in a comparatively small image formation unit or a cleaning unit with a small toner collection amount or when a comparatively large collection box cannot be placed, it may also be advisable from maintenance of the unit, etc., to use means placing the collection box integral with the main unit of the cleaning unit.
Apart from the cleaning unit for an image support as described above, for example, an electrophotographic copier disclosed in Japanese Patent Laid-Open No. Sho 59-168467 has a plurality of photosensitive drums placed corresponding to a paper transporter and transfers overlapped color toner images to a sheet of paper supported by the paper transporter for making a full color copy. The electrophotographic copier comprises means for writing marks to control toner image density, color displacement, etc., onto a conveyer belt member forming a part of the paper transporter and means for reading the mark image density. It reads the marks of the toner images formed on the belt for adjusting the image density, senses color displacement among the marks transferred from the photosensitive drums, and rewrites control information in a controller, then removes the marks by the cleaning unit for preventing extra toner from adhering to paper.
Thus, the electrophotographic copier for making a color copy as described above has a cleaning unit for removing toner placed for a conveyer belt member forming a part of a paper transporter. However, since the amount of collected toner is comparatively small at the cleaning unit placed for the belt member, if a collection box is combined with the main unit, space in which the vessel can be housed is limited. Further, the form of the storage vessel is limited because of space restriction as described above, also affecting the structure of a device for sensing that the vessel fills with toner, making it difficult to accurately sense it.